Case study: Feed system retrofit at an Australian gold operation
FLS has supported thickener performance upgrade at one of Australia’s largest gold mines for several years now.
When the mine first approached the engineering company, it was operating third-party 34-metre diameter leach feed and 44-metre diameter tailings thickeners, and nameplate capacity was 700 tonnes per hour (tph).
“We initially upgraded the leach feed thickener, installing an E-DUC® dilution system and E-Volute feedwell,” FLS regional product line manager for dewatering Anson Gilbert said.
“This increased leach feed thickener underflow density from 48 per cent to 54 per cent solids at 850 tph of feed solids, resulting in significant savings in both lime and cyanide consumption, as well as increasing carbon in leach (CIL) residence times.
Flocculant consumption also fell by 34 per cent on a gram/tonne basis. Return on investment was achieved in less than six months.”
Discover more about the initial optimisation project here.
The mine successfully operated with this upgraded set-up for several years. Over time, however, the thickener started to bottleneck the process, and the mine again approached FLS to help
“The mine’s proposal was to swap the duties of the 34-metre leach feed thickener and 44-metre tailings thickener,” Gilbert said.
“When we were called in, we set about analysing the idea with a comprehensive program of onsite test work, process evaluation and structural analysis of both thickener bridges.”
Through this work, the FLS team observed continuous pluming in the leach feed thickener in proximity to the overflow launders – with solid particles in the overflow visible at elevated throughputs – while faster settling rates and compaction times were seen in the tailings thickener.
“We were therefore able to prove the viability of swapping thickener duties to unlock additional thickener capacity,” Gilbert said.
“The faster settling tailings material could be treated in the smaller thickener, meaning the additional unit area required for the leach feed application could be obtained by using the larger thickener.”
FLS recommended installing P-DUC mechanisms on both thickeners and an E-Volute™ feedwell on the 44-metre thickener.
The engineering team also recommended a larger feed box to allow for increased throughput and improved deaeration of the feed.
As a result of the upgrade, thickener throughput has increased from 1060 tph to 1160 tph, without any increase in flocculant consumption on a gram/tonne basis
There is also now no visible pluming or particle carryover in either of the thickeners overflow.
“Thickeners are no longer the bottleneck to performance. By increasing throughput and maintaining the same fixed costs, we also enhanced profitability, and payback has been achieved in under 12 months,” Gilbert said.
The value of thickener upgrades
“The retrofit demonstrates the potential improvements that a thickener upgrade can bring to an operation,” David Williams said.
“In both units, we achieved a large improvement in solid-liquid separation, which facilitated a further flowsheet change and removed a customer pain point.”
Overall, the upgrade resulted in a 9 per cent increase in plant capacity – allowing for reduced fixed cost per ounce.
This project also demonstrates the mutual benefits thickener upgrades can bring to a mine’s profitability and environmental performance. Specific sustainability wins included:
- Increasing the underflow density from the leach feed thickener allows for additional residence time in the CIL circuit, improving recovery at a given throughput. This increases the production of gold without increasing the amount of ore mined.
- The underflow water ratio in the tailings thickener dropped from 0.85 tonnes water to 0.75 tonnes water per tonne of solids processed – an 11 per cent reduction in water going to the tailings dam (even with the higher tonnage).
These benefits align with our MissionZero sustainability program to drive sustainable productivity in mining – and demonstrate the complementary value this sort of project can bring to a mine’s productivity and environmental performance.
“As sustainability becomes an ever-important element in the performance of minerals processing operations, we believe the value of such projects will become increasingly important, as mining companies seek to meet both financial and environmental goals.", said David Williams.
“We are committed to supporting the industry on this journey and, through our MissionZero program, are working with our customers and other partners to build a truly sustainable mining industry.”
Created: 15 July 2022
Updated: October 2024
